From Matt Cooper's recounting of his famous conversation with I. Lewis Libby on July 12, 2003:

That afternoon, we talked a bit on background and off the record, and he gave me an on-the-record quote distancing Cheney from Wilson's fact-finding trip to Africa for the CIA. In fact, he was so eager to distance his boss from Wilson that a few days later, he called to rebuke me for not having used the whole quote in the piece.

Why is this important?  Because the Plame disclosures weren't about killing the messenger--they were about killing the message.  The contents of the Plame "smear" were that his wife got him the job sending him to Africa and the Vice President had nothing to do with it.  The focus has been on the idea that it was a boondogle for Wilson.  That hasn't been the point.  The point has been to distance the Vice President from the fact-finding mission--a mission associated with the faked Niger documents.  The Vice President's staff was trying to disassociate him from the Niger dossier.  It will be up to the press to link him to it.